merge-recursive: do not use on-file index when not needed.

This revamps the merge-recursive implementation following the
outline in:

	Message-ID: <7v8xgileza.fsf@assigned-by-dhcp.cox.net>

There is no need to write out the index until the very end just
once from merge-recursive.  Also there is no need to write out
the resulting tree object for the simple case of merging with a
single merge base.

Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/merge-recursive.c b/merge-recursive.c
index aab4c3458884455608466d377de8942f82b04aca..52370213092c13bd02988493b21489ec61fb2593 100644 (file)
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -110,35 +110,6 @@ static void output_commit_title(struct commit *commit)
        }
 }
 
-static const char *current_index_file = NULL;
-static const char *original_index_file;
-static const char *temporary_index_file;
-static int cache_dirty = 0;
-
-static int flush_cache(void)
-{
-       /* flush temporary index */
-       struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
-       int fd = hold_lock_file_for_update(lock, current_index_file, 1);
-       if (write_cache(fd, active_cache, active_nr) ||
-                       close(fd) || commit_lock_file(lock))
-               die ("unable to write %s", current_index_file);
-       discard_cache();
-       cache_dirty = 0;
-       return 0;
-}
-
-static void setup_index(int temp)
-{
-       current_index_file = temp ? temporary_index_file: original_index_file;
-       if (cache_dirty) {
-               discard_cache();
-               cache_dirty = 0;
-       }
-       unlink(temporary_index_file);
-       discard_cache();
-}
-
 static struct cache_entry *make_cache_entry(unsigned int mode,
                const unsigned char *sha1, const char *path, int stage, int refresh)
 {
@@ -167,9 +138,6 @@ static int add_cacheinfo(unsigned int mode, const unsigned char *sha1,
                const char *path, int stage, int refresh, int options)
 {
        struct cache_entry *ce;
-       if (!cache_dirty)
-               read_cache_from(current_index_file);
-       cache_dirty++;
        ce = make_cache_entry(mode, sha1 ? sha1 : null_sha1, path, stage, refresh);
        if (!ce)
                return error("cache_addinfo failed: %s", strerror(cache_errno));
@@ -187,26 +155,6 @@ static int add_cacheinfo(unsigned int mode, const unsigned char *sha1,
  */
 static int index_only = 0;
 
-static int git_read_tree(struct tree *tree)
-{
-       int rc;
-       struct object_list *trees = NULL;
-       struct unpack_trees_options opts;
-
-       if (cache_dirty)
-               die("read-tree with dirty cache");
-
-       memset(&opts, 0, sizeof(opts));
-       object_list_append(&tree->object, &trees);
-       rc = unpack_trees(trees, &opts);
-       cache_tree_free(&active_cache_tree);
-
-       if (rc == 0)
-               cache_dirty = 1;
-
-       return rc;
-}
-
 static int git_merge_trees(int index_only,
                           struct tree *common,
                           struct tree *head,
@@ -216,11 +164,6 @@ static int git_merge_trees(int index_only,
        struct object_list *trees = NULL;
        struct unpack_trees_options opts;
 
-       if (!cache_dirty) {
-               read_cache_from(current_index_file);
-               cache_dirty = 1;
-       }
-
        memset(&opts, 0, sizeof(opts));
        if (index_only)
                opts.index_only = 1;
@@ -236,39 +179,37 @@ static int git_merge_trees(int index_only,
 
        rc = unpack_trees(trees, &opts);
        cache_tree_free(&active_cache_tree);
-
-       cache_dirty = 1;
-
        return rc;
 }
 
+static int unmerged_index(void)
+{
+       int i;
+       for (i = 0; i < active_nr; i++) {
+               struct cache_entry *ce = active_cache[i];
+               if (ce_stage(ce))
+                       return 1;
+       }
+       return 0;
+}
+
 static struct tree *git_write_tree(void)
 {
        struct tree *result = NULL;
 
-       if (cache_dirty) {
-               unsigned i;
-               for (i = 0; i < active_nr; i++) {
-                       struct cache_entry *ce = active_cache[i];
-                       if (ce_stage(ce))
-                               return NULL;
-               }
-       } else
-               read_cache_from(current_index_file);
+       if (unmerged_index())
+               return NULL;
 
        if (!active_cache_tree)
                active_cache_tree = cache_tree();
 
        if (!cache_tree_fully_valid(active_cache_tree) &&
-                       cache_tree_update(active_cache_tree,
-                               active_cache, active_nr, 0, 0) < 0)
+           cache_tree_update(active_cache_tree,
+                             active_cache, active_nr, 0, 0) < 0)
                die("error building trees");
 
        result = lookup_tree(active_cache_tree->sha1);
 
-       flush_cache();
-       cache_dirty = 0;
-
        return result;
 }
 
@@ -331,10 +272,7 @@ static struct path_list *get_unmerged(void)
        int i;
 
        unmerged->strdup_paths = 1;
-       if (!cache_dirty) {
-               read_cache_from(current_index_file);
-               cache_dirty++;
-       }
+
        for (i = 0; i < active_nr; i++) {
                struct path_list_item *item;
                struct stage_data *e;
@@ -469,9 +407,6 @@ static int remove_file(int clean, const char *path, int no_wd)
        int update_working_directory = !index_only && !no_wd;
 
        if (update_cache) {
-               if (!cache_dirty)
-                       read_cache_from(current_index_file);
-               cache_dirty++;
                if (remove_file_from_cache(path))
                        return -1;
        }
@@ -1105,9 +1040,7 @@ static int merge_trees(struct tree *head,
                    sha1_to_hex(head->object.sha1),
                    sha1_to_hex(merge->object.sha1));
 
-       *result = git_write_tree();
-
-       if (!*result) {
+       if (unmerged_index()) {
                struct path_list *entries, *re_head, *re_merge;
                int i;
                path_list_clear(&current_file_set, 1);
@@ -1128,17 +1061,11 @@ static int merge_trees(struct tree *head,
                        if (!process_entry(path, e, branch1, branch2))
                                clean = 0;
                }
-               if (cache_dirty)
-                       flush_cache();
 
                path_list_clear(re_merge, 0);
                path_list_clear(re_head, 0);
                path_list_clear(entries, 1);
 
-               if (clean || index_only)
-                       *result = git_write_tree();
-               else
-                       *result = NULL;
        } else {
                clean = 1;
                printf("merging of trees %s and %s resulted in %s\n",
@@ -1146,6 +1073,8 @@ static int merge_trees(struct tree *head,
                       sha1_to_hex(merge->object.sha1),
                       sha1_to_hex((*result)->object.sha1));
        }
+       if (index_only)
+               *result = git_write_tree();
 
        return clean;
 }
@@ -1170,10 +1099,10 @@ static int merge(struct commit *h1,
                 const char *branch1,
                 const char *branch2,
                 int call_depth /* =0 */,
-                struct commit *ancestor /* =None */,
+                struct commit_list *ca,
                 struct commit **result)
 {
-       struct commit_list *ca = NULL, *iter;
+       struct commit_list *iter;
        struct commit *merged_common_ancestors;
        struct tree *mrtree;
        int clean;
@@ -1182,10 +1111,10 @@ static int merge(struct commit *h1,
        output_commit_title(h1);
        output_commit_title(h2);
 
-       if (ancestor)
-               commit_list_insert(ancestor, &ca);
-       else
-               ca = reverse_commit_list(get_merge_bases(h1, h2, 1));
+       if (!ca) {
+               ca = get_merge_bases(h1, h2, 1);
+               ca = reverse_commit_list(ca);
+       }
 
        output("found %u common ancestor(s):", commit_list_count(ca));
        for (iter = ca; iter; iter = iter->next)
@@ -1211,6 +1140,7 @@ static int merge(struct commit *h1,
                 * merge_trees has always overwritten it: the commited
                 * "conflicts" were already resolved.
                 */
+               discard_cache();
                merge(merged_common_ancestors, iter->item,
                      "Temporary merge branch 1",
                      "Temporary merge branch 2",
@@ -1223,25 +1153,21 @@ static int merge(struct commit *h1,
                        die("merge returned no commit");
        }
 
+       discard_cache();
        if (call_depth == 0) {
-               setup_index(0 /* $GIT_DIR/index */);
+               read_cache();
                index_only = 0;
-       } else {
-               setup_index(1 /* temporary index */);
-               git_read_tree(h1->tree);
+       } else
                index_only = 1;
-       }
 
        clean = merge_trees(h1->tree, h2->tree, merged_common_ancestors->tree,
                            branch1, branch2, &mrtree);
 
-       if (!ancestor && (clean || index_only)) {
+       if (index_only) {
                *result = make_virtual_commit(mrtree, "merged tree");
                commit_list_insert(h1, &(*result)->parents);
                commit_list_insert(h2, &(*result)->parents->next);
-       } else
-               *result = NULL;
-
+       }
        return clean;
 }
 
@@ -1277,19 +1203,16 @@ static struct commit *get_ref(const char *ref)
 
 int main(int argc, char *argv[])
 {
-       static const char *bases[2];
+       static const char *bases[20];
        static unsigned bases_count = 0;
        int i, clean;
        const char *branch1, *branch2;
        struct commit *result, *h1, *h2;
+       struct commit_list *ca = NULL;
+       struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
+       int index_fd;
 
        git_config(git_default_config); /* core.filemode */
-       original_index_file = getenv(INDEX_ENVIRONMENT);
-
-       if (!original_index_file)
-               original_index_file = xstrdup(git_path("index"));
-
-       temporary_index_file = xstrdup(git_path("mrg-rcrsv-tmp-idx"));
 
        if (argc < 4)
                die("Usage: %s <base>... -- <head> <remote> ...\n", argv[0]);
@@ -1313,18 +1236,18 @@ int main(int argc, char *argv[])
        branch2 = better_branch_name(branch2);
        printf("Merging %s with %s\n", branch1, branch2);
 
-       if (bases_count == 1) {
-               struct commit *ancestor = get_ref(bases[0]);
-               clean = merge(h1, h2, branch1, branch2, 0, ancestor, &result);
-       } else
-               clean = merge(h1, h2, branch1, branch2, 0, NULL, &result);
+       index_fd = hold_lock_file_for_update(lock, get_index_file(), 1);
 
-       if (cache_dirty)
-               flush_cache();
+       for (i = 0; i < bases_count; i++) {
+               struct commit *ancestor = get_ref(bases[i]);
+               ca = commit_list_insert(ancestor, &ca);
+       }
+       clean = merge(h1, h2, branch1, branch2, 0, ca, &result);
+
+       if (active_cache_changed &&
+           (write_cache(index_fd, active_cache, active_nr) ||
+            close(index_fd) || commit_lock_file(lock)))
+                       die ("unable to write %s", get_index_file());
 
        return clean ? 0: 1;
 }
-
-/*
-vim: sw=8 noet
-*/